The present invention is directed to an expansion dowel assembly for securement in thin-walled structural components with the assembly including a dowel member having elongated arms which buckle radially outwardly when the dowel member is collapsed in the axial direction. A flange is located at one end of the arms and the arms are interconnected at the other end by junction member. Force applying means can be arranged at the junction member for effecting the axial collapse of the dowel member.
For providing an attachment to thin-walled structural components accessible only from one side, such as plates or hollow receiving materials, so-called cavity dowels are used. To effect anchoring such dowels are introduced into a receiving bore or opening until the abutment of a flange on the dowel contacts the surface of the receiving material. The dowel is dimensioned so that the larger portion of its length extends through the receiving material and into a cavity or hollow space behind the material. Subsequently, the dowel is collapsed in the axial direction such as by a special tool or a threaded bolt, so that expansion arms forming the dowel buckle radially outwardly and grip behind the receiving material. The extent of this collapsing operation is not visible from the exterior, accordingly, certain inferences must be drawn with regard to the anchored state of the dowel based on the increase in resistance to its deformation.
When the above-mentioned expansion dowel is used in soft receiving materials, such as plastics or the like, it has been noted that an overexpansion of the dowel is possible, which may result in damage to the receiving material and the dowel. Usually such damage is not recognizable from the exterior and, therefore, can lead to failure when a load is applied to the dowel